In recent years, products having an air cleaning effect, disinfection effects, or relaxation effects (for example, an air conditioner or an air cleaner) have been increasing. These products achieve the effects by diffusing ions or mist (tiny drops of water), mist containing a fragrant component or a medicinal component, or microparticles such as water vapor in a room. In designing these products, there is a need for a method for determining local concentrations of microparticles discharged into a room space by a numerical analysis. For example, Japanese Patent Laying-Open No. 2004-028518 (Patent Document 1) discloses a method for designing a clean room that can appropriately reduce fine particles by monitoring the number distribution of fine particles in the clean room.
A flow field analysis system that analyzes a flow field in a room to determine local directions, local velocities, and local temperatures of air currents has been commercialized. A known indoor flow field analysis system includes the steps of constructing an analytical model in which a room is divided into microelements to analyze a flow field in the room, inputting a boundary condition to simulate the flow field with the analytical model, analyzing the analytical model with the boundary condition to determine the flow field defined by the directions, the velocities, and the temperatures of air currents at the microelements.
A known flow field analysis system employs a mass conservation formula, a momentum conservation formula, a turbulent energy conservation formula, and a turbulent dissipation conservation formula to determine the flow field. In addition to these conservation formulae, an energy conservation formula is employed to determine the temperature distribution.
This known analysis system in combination with a diffusion equation of a material allows the determination of indoor local concentrations of microparticle contaminants having a stable composition (for example, CO2, NO2, or water vapor) in the air and the analysis of diffusive behavior of the microparticles in the room. However, many equations must be solved. This makes the computation complicated and causes many computational errors. Thus, the concentration distribution could not be determined accurately. Furthermore, since these equations are defined theoretically, the theoretical diffusive behavior of particles may be different from the actual diffusive behavior of the particles under a certain condition.
Another method analyzes a flow field in a room to determine local ages of air in the room and thereby determine the age-of-air distribution in a living room. This method further includes a step of determining the age-of-air distribution in the room on the basis of the conventional analysis of the flow field in the room. For example, Japanese Patent Laying-Open No. 2004-101058 (Patent Document 2) discloses an analysis system for designing a ventilation system having an improved ventilation efficiency. This system explicitly defines the effects of a plurality of air outlets and air inlets on the age of air and the life expectancy of air at a point of measurement in a room.
Patent Document 1: Japanese Patent Laying-Open No. 2004-028518
Patent Document 2: Japanese Patent Laying-Open No. 2004-101058